Did You Know?
There are more than 20 different types of reticular fibers in the human body.
Categorized under loose connective tissues, reticular connective tissues are also named as reticular fibers, which are an essential part of the body's tissue framework. The units that together form these fibers are called reticular cells or fibroblasts. These fibers are made up of collagen and glycoproteins. They have a thin and branching appearance, a diameter of around 150 nanometers, and are almost invisible in histological sections. However, they can be viewed microscopically, after impregnation with silver stains. This affinity of the fibers for silver staining is known as argyrophilia. They are also impregnated with PAS reaction because of the glycoproteins present in them. Reticular fibers are made up of collagen type III.
Reticular connective tissues are arranged along with different cells in various organs like bone marrow, lymph nodes, spleen, liver, kidneys, and even under the skin. These tissues have a peculiar feature; they never exist alone. Rather, you will always find reticular cells and fibers in association with other cells. These fibers are a significant part of most of the fibrous connective tissues, and are always seen to be the dominant ones. This tissue type forms a structural framework (fibrous cartilage) for organ cells in many organs and tissues.
When these tissues are viewed closely, they are found to be in series of branching threads. Reticular fibers present in the tissues are fragile, and together bond to form a meshwork or a fibrous skeleton (stroma). To get a microscopic view of these cells, special stains are used, as they are not easily viewed even through microscopes. For example, when silver stains are used in histological sections, the reticular fibers appear like black threads, and the coarse collagen fibers appear reddish-brown. The two are believed to be different from one another due to the different staining characteristics. The tissue structure looks quite similar to that of elastic connective tissue. The only difference is that collagen fibers are branched in reticular tissues, whereas they lie parallel in the elastic ones. The structural framework of collagen lattice in reticular tissues provides great strength and support to the organs of the human body system.
Reticular fibers also experience breakdown, and are recycled and replaced by the new ones. The fibres are destroyed when they stop functioning, and new strands of collagen are generated to replace the damaged ones. The formation of new reticular fibers, and maintenance of the existing ones, is handled by specialized reticular cells.
- The most important function of this tissue is to provide support to the organs, tissues, and individual cells like adipose tissues and muscles.
- Reticular fibers form a dense structure, and hold together the cells of smooth muscle tissue, and also help in the formation of basement membrane.
- The mesh-like network formed by the fibers is useful for those organs and tissues, which deal with processes like cell movement and diffusion.
- Reticular tissue forms a supporting wall for blood vessels, and also maintains a strong network for other cell types, as well as for skeletal and nerve fibers.
- Other functions include filtration of various body fluids in organs like spleen and lymph nodes.
- With respect to an organ, reticular fibers are associated with the liver cells (hepatocytes), and are visible when impregnated with silver stain preparation.
- The fibers support each individual sheet of these cells.
- Reticular connective tissues are the only supporting tissues that are involved in the above process.
- While supporting the liver cells, the network enables exchange of content between the hepatocytes and blood.
On a concluding note, it can be said that reticular connective tissues form a basic supportive framework that is extremely crucial for the functioning of important organs, and for other associated processes like locomotion and muscle movement.